Lipocortin 1 and the control of cPLA2 activity in A549 cells. Glucocorticoids block EGF stimulation of cPLA2 phosphorylation

Therapeutic Potential of Annexin A1 Modulation in Kidney and Cardiovascular Disorders

Renal and cardiovascular disorders are very prevalent and associated with significant morbidity and mortality. Among diverse pathogenic mechanisms, the dysregulation of immune and inflammatory responses plays an essential role in such disorders. Consequently, the discovery of Annexin A1, as a glucocorticoid-inducible anti-inflammatory protein, has fueled investigation of its role in renal and cardiovascular pathologies. Indeed, with respect to the kidney, its role has been examined in diverse renal pathologies, including acute kidney injury, diabetic nephropathy, immune-mediated nephropathy, drug-induced kidney injury, kidney stone formation, and renal cancer. Regarding the cardiovascular system, major areas of investigation include the role of Annexin A1 in vascular abnormalities, atherosclerosis, and myocardial infarction. Thus, this review briefly describes major structural and functional features of Annexin A1 followed by a review of its role in pathologies of the kidney and the cardiovascular system, as well as the therapeutic potential of its modulation for such disorders.

Novel Role for the AnxA1-Fpr2/ALX Signaling Axis as a Key Regulator of Platelet Function to Promote Resolution of Inflammation

Supplemental Digital Content is available in the text.

Background:

Ischemia reperfusion injury (I/RI) is a common complication of cardiovascular diseases. Resolution of detrimental I/RI-generated prothrombotic and proinflammatory responses is essential to restore homeostasis. Platelets play a crucial part in the integration of thrombosis and inflammation. Their role as participants in the resolution of thromboinflammation is underappreciated; therefore we used pharmacological and genetic approaches, coupled with murine and clinical samples, to uncover key concepts underlying this role.

Methods:

Middle cerebral artery occlusion with reperfusion was performed in wild-type or annexin A1 (AnxA1) knockout (AnxA1^−/−) mice. Fluorescence intravital microscopy was used to visualize cellular trafficking and to monitor light/dye–induced thrombosis. The mice were treated with vehicle, AnxA1 (3.3 mg/kg), WRW4 (1.8 mg/kg), or all 3, and the effect of AnxA1 was determined in vivo and in vitro.

Results:

Intravital microscopy revealed heightened platelet adherence and aggregate formation post I/RI, which were further exacerbated in AnxA1^−/− mice. AnxA1 administration regulated platelet function directly (eg, via reducing thromboxane B₂ and modulating phosphatidylserine expression) to promote cerebral protection post-I/RI and act as an effective preventative strategy for stroke by reducing platelet activation, aggregate formation, and cerebral thrombosis, a prerequisite for ischemic stroke. To translate these findings into a clinical setting, we show that AnxA1 plasma levels are reduced in human and murine stroke and that AnxA1 is able to act on human platelets, suppressing classic thrombin-induced inside-out signaling events (eg, Akt activation, intracellular calcium release, and Ras-associated protein 1 [Rap1] expression) to decrease α_IIbβ₃ activation without altering its surface expression. AnxA1 also selectively modifies cell surface determinants (eg, phosphatidylserine) to promote platelet phagocytosis by neutrophils, thereby driving active resolution. (n=5–13 mice/group or 7–10 humans/group.)

Conclusions:

AnxA1 affords protection by altering the platelet phenotype in cerebral I/RI from propathogenic to regulatory and reducing the propensity for platelets to aggregate and cause thrombosis by affecting integrin (α_IIbβ₃) activation, a previously unknown phenomenon. Thus, our data reveal a novel multifaceted role for AnxA1 to act both as a therapeutic and a prophylactic drug via its ability to promote endogenous proresolving, antithromboinflammatory circuits in cerebral I/RI. Collectively, these results further advance our knowledge and understanding in the field of platelet and resolution biology.

The Anti-allergic Cromones: Past, Present, and Future

The anti-allergic cromones were originally synthesized in the 1960s by Fisons Plc, and the first drug to emerge from this program, disodium cromoglycate was subsequently marketed for the treatment of asthma and other allergic conditions. Whilst early studies demonstrated that the ability of the cromones to prevent allergic reactions was due to their 'mast cell stabilizing' properties, the exact pharmacological mechanism by which this occurred, remained a mystery. Here, we briefly review the history of these drugs, recount some aspects of their pharmacology, and discuss two new explanations for their unique actions. We further suggest how these findings could be used to predict further uses for the cromones.

Multiplicity of Glucocorticoid Action in Inhibiting Allograft Rejection

Glucocorticoids (GCs) are used as immunosuppressive and antiinflammatory agents in organ transplantation and in treating autoimmune diseases and inflammatory disorders. GCs were shown to exert their antiproliferative effects directly through blockade of certain elements of an early membrane-associated signal transduction pathway, modulation of the expression of select adhesion molecules, and by suppression of cytokine synthesis and action. GCs may act indirectly by inducing lipocortin synthesis, which in turn, inhibits arachidonic acid release from membrane-bound stores, and also by inducing transforming growth factor (TGF)-β expression that subsequently blocks cytokine synthesis and T cell activation. Furthermore, by preferentially inhibiting the production of Th1 cytokines, GCs may enhance Th2 cell activity and, hence, precipitate a long-lasting state of tolerance through a preferential promotion of a Th2 cytokine-secreting profile. In exerting their antiproliferative effects, GCs influence both transcriptional and posttranscriptional events by binding their cytosolic receptor (GR), which subsequently binds the promoter region of cytokine genes on select DNA sites compatible with the GCs responsible elements (GRE) motif. In addition to direct DNA binding, GCs may also directly bind to, and hence antagonize, nuclear factors required for efficient gene expression, thereby markedly reducing transcriptional rate. The pleiotrophy of the GCs action, coupled with the diverse experimental conditions employed in assessing the GCs effects, indicate that GCs may utilize more than one mechanism in inhibiting T cell activation, and warrant careful scrutiny in assigning a mechanism by which GCs exert their antiproliferative effects. © 1998 Elsevier Science Inc.

Highly unsaturated fatty acids (HUFA) mediate and monitor food's impact on health

A hyperbolic, saturable, competitive dynamic of ligand binding to metabolic enzymes and lipid mediator receptors gives non-linear dose-response interactions that need careful management when planning or interpreting nutrient-based interventions. Relatively indiscriminate metabolism during accumulation of HUFA from n-3 and n-6 nutrients allows the amounts of n-3 and n-6 nutrients to determine the HUFA balance accumulated in tissue phospholipids. However, when HUFA-based eicosanoid actions are more intense with n-6 than n-3 mediators, they cause healthy physiology to shift toward pathophysiology. The proportion of n-6 in tissue HUFA directly relates to the severity of conditions caused by excessive n-6 actions. In the absence of n-3 nutrients, dietary linoleate (18:2n-6) has a very narrow therapeutic window below 1 percent of food energy, and it is widened by n-3 nutrients. The predictable quantitative dynamics of competing n-3 and n-6 nutrients allows design of successful preventive nutrition protocols that confirm and extend the epidemiologically observed benefits of n-3 nutrients.

A Mechanistic Basis for the Beneficial Effects of Caloric Restriction On Longevity and Disease: Consequences for the Interpretation of Rodent Toxicity Studies

Caloric restriction in rodents has been repeatedly shown to increase life span while reducing the severity and retarding the onset of both spontaneous and chemically induced neoplasms. These effects of caloric restriction are associated with a spectrum of biochemical and physiological changes that characterize the organism's adaptation to reduced caloric intake and provide the mechanistic basis for caloric restriction's effect on longevity. Here, we review evidence suggesting that the primary adaptation appears to be a rhythmic hypercorticism in the absence of elevated adrenocorticotropin (ACTH) levels. This characteristic hypercorticism evokes a spectrum of responses, including reduced body temperature and increased metabolic efficiency, decreased mitogenic response coupled with increased rates of apoptosis, reduced inflammatory response, reduced oxidative damage to proteins and DNA, reduced reproductive capacity, and altered drug-metabolizing enzyme expression. The net effect of these changes is to (1) decrease growth and metabolism in peripheral tissues to spare energy for central functions, and (2) increase the organism's capacity to withstand stress and chemical toxicity. Thus, caloric restriction research has uncovered an evolutionary mechanism that provides rodents with an adaptive advantage in conditions of fluctuating food supply. During periods of abundance, body growth and fecundity are favored over endurance and longevity. Conversely, during periods of famine, reproductive performance and growth are sacrificed to ensure survival of individuals to breed in better times. This phenomena can be observed in rodent populations that are used in toxicity testing. Improvements over the last 30 years in animal husbandry and nutrition, coupled with selective breeding for growth and fecundity, have resulted in several strains now exhibiting larger animals with reduced survival and increased incidence of background lesions. The mechanistic data from caloric restriction studies suggest that these large animals will also be more susceptible to chemically induced toxicity. This creates a problem in comparing tests performed on animals of different weights and comparing data generated today with the historical database. The rational use of caloric restriction to control body weight to within preset guidelines is a possible way of alleviating this problem.

Role of intracellular and extracellular annexin A1 in migration and invasion of human pancreatic carcinoma cells

BACKGROUND

Annexin A1 (ANXA1), a 37 kDa multifunctional protein, is over-expressed in tissues from patients of pancreatic carcinoma (PC) where the protein seems to be associated with malignant transformation and poor prognosis.

METHODS

The expression and localization of ANXA1 in MIA PaCa-2, PANC-1, BxPC-3 and CAPAN-2 cells were detected by Western Blotting and Immunofluorescence assay. Expression and activation of Formyl Peptide Receptors (FPRs) were shown through flow cytometry/PCR and FURA assay, respectively. To investigate the role of ANXA1 in PC cell migration and invasion, we performed in vitro wound-healing and matrigel invasion assays.

RESULTS

In all the analyzed PC cell lines, a huge expression and a variable localization of ANXA1 in sub-cellular compartments were observed. We confirmed the less aggressive phenotype of BxPC-3 and CAPAN-2 compared with PANC-1 and MIA PaCa-2 cells, through the evaluation of Epithelial-Mesenchymal Transition (EMT) markers. Then, we tested MIA PaCa-2 and PANC-1 cell migration and invasiveness rate which was inhibited by specific ANXA1 siRNAs. Both the cell lines expressed FPR-1 and -2. Ac2-26, an ANXA1 mimetic peptide, induced intracellular calcium release, consistent with FPR activation, and significantly increased cell migration/invasion rate. Interestingly, in MIA PaCa-2 cells we found a cleaved form of ANXA1 (33 kDa) that localizes at cellular membranes and is secreted outside the cells, as confirmed by MS analysis. The importance of the secreted form of ANXA1 in cellular motility was confirmed by the administration of ANXA1 blocking antibody that inhibited migration and invasion rate in MIA PaCa-2 but not in PANC-1 cells that lack the 33 kDa ANXA1 form and show a lower degree of invasiveness. Finally, the treatment of PANC-1 cells with MIA PaCa-2 supernatants significantly increased the migration rate of these cells.

CONCLUSION

This study provides new insights on the role of ANXA1 protein in PC progression. Our findings suggest that ANXA1 protein could regulate metastasis by favouring cell migration/invasion intracellularly, as cytoskeleton remodelling factor, and extracellularly like FPR ligand.

Macrophage migration inhibitory factor counter-regulates dexamethasone-induced annexin 1 expression and influences the release of eicosanoids in murine macrophages

Macrophage migration inhibitory factor (MIF), a pro-inflammatory cytokine and glucocorticoid (GC) counter-regulator, has emerged as an important modulator of inflammatory responses. However, the molecular mechanisms of MIF counter-regulation of GC still remain incomplete. In the present study, we investigated whether MIF mediated the counter-regulation of the anti-inflammatory effect of GC by affecting annexin 1 in RAW 264.7 macrophages. We found that stimulation of RAW 264.7 macrophages with lipopolysaccharide (LPS) resulted in down-regulation of annexin 1, while GC dexamethasone (Dex) or Dex plus LPS led to significant up-regulation of annexin 1 expression. RNA interference-mediated knockdown of intracellular MIF increased annexin 1 expression with or without incubation of Dex, whereas Dex-induced annexin 1 expression was counter-regulated by the exogenous application of recombinant MIF. Moreover, recombinant MIF counter-regulated, in a dose-dependent manner, inhibition of cytosolic phospholipase A2α (cPLA2α) activation and prostaglandin E2 (PGE2 ) and leukotriene B4 (LTB4 ) release by Dex in RAW 264.7 macrophages stimulated with LPS. Endogenous depletion of MIF enhanced the effects of Dex, reflected by further decease of cPLA2α expression and lower PGE2 and LTB4 release in RAW 264.7 macrophages. Based on these data, we suggest that MIF counter-regulates Dex-induced annexin 1 expression, further influencing the activation of cPLA2α and the release of eicosanoids. These findings will add new insights into the mechanisms of MIF counter-regulation of GC.

Annexin 1: a glucocorticoid-inducible protein that modulates inflammatory pain

Annexin 1, a glucocorticoid (GC)-inducible protein, can play an important role via formyl peptide receptor like 1 (FPR2/ALX, also known as FPRL1) in inflammatory pain modulation. The aim of this review is to analyze different lines of evidence for the role of ANXA1 with different mechanisms on inflammatory pain and describe the profile of ANXA1 as a potential analgesic. A Medline (PUBMED) search using the terms 'Annexin 1 distribution OR expression, FPR2/ALX distribution OR expression, Annexin 1 AND pain, Annexin 1 AND FPR2/ALX AND pain' was performed. Articles with a publication date up to Nov. 1st, 2012 were included. The antinociception of ANXA1 has been evaluated in diverse pain models. It has been suggested that ANXA1 may exerts its action via: (1) inhibiting vital cytokines involved in pain transmission, (2) inhibiting neutrophil accumulation through preventing transendothelial migration via an interaction with formyl peptide receptors, (3) facilitating tonic opioid release from neutrophil in inflammatory site, (4) interrupting the peripheral nociceptive transmission by suppressing neuronal excitability. In general, ANXA1 is a potential mediator for anti-nociception and the role with its receptor constitute attractive targets for developing anesthesia and analgesic drugs, and their interaction may prove to be a useful strategy to treat inflammatory pain.

Annexin A1 induces skeletal muscle cell migration acting through formyl peptide receptors

Annexin A1 (ANXA1, lipocortin-1) is a glucocorticoid-regulated 37-kDa protein, so called since its main property is to bind (i.e. to annex) to cellular membranes in a Ca(2+)-dependent manner. Although ANXA1 has predominantly been studied in the context of immune responses and cancer, the protein can affect a larger variety of biological phenomena, including cell proliferation and migration. Our previous results show that endogenous ANXA1 positively modulates myoblast cell differentiation by promoting migration of satellite cells and, consequently, skeletal muscle differentiation. In this work, we have evaluated the hypothesis that ANXA1 is able to exert effects on myoblast cell migration acting through formyl peptide receptors (FPRs) following changes in its subcellular localization as in other cell types and tissues. The analysis of the subcellular localization of ANXA1 in C2C12 myoblasts during myogenic differentiation showed an interesting increase of extracellular ANXA1 starting from the initial phases of skeletal muscle cell differentiation. The investigation of intracellular Ca(2+) perturbation following exogenous administration of the ANXA1 N-terminal derived peptide Ac2-26 established the engagement of the FPRs which expression in C2C12 cells was assessed by qualitative PCR. Wound healing assay experiments showed that Ac2-26 peptide is able to increase migration of C2C12 skeletal muscle cells and to induce cell surface translocation and secretion of ANXA1. Our results suggest a role for ANXA1 as a highly versatile component in the signaling chains triggered by the proper calcium perturbation that takes place during active migration and differentiation or membrane repair since the protein is strongly redistributed onto the plasma membranes after an rapid increase of intracellular levels of Ca(2+). These properties indicate that ANXA1 may be involved in a novel repair mechanism for skeletal muscle and may have therapeutic implications with respect to the development of ANXA1 mimetics.

Annexin A1: novel roles in skeletal muscle biology

Annexin A1 (ANXA1, lipocortin-1) is the first characterized member of the annexin superfamily of proteins, so called since their main property is to bind (i.e., to annex) to cellular membranes in a Ca(2+) -dependent manner. ANXA1 has been involved in a broad range of molecular and cellular processes, including anti-inflammatory signalling, kinase activities in signal transduction, maintenance of cytoskeleton and extracellular matrix integrity, tissue growth, apoptosis, and differentiation. New insights show that endogenous ANXA1 positively modulates myoblast cell differentiation by promoting migration of satellite cells and, consequently, skeletal muscle differentiation. This suggests that ANXA1 may contribute to the regeneration of skeletal muscle tissue and may have therapeutic implications with respect to the development of ANXA1 mimetics.

Do annexins participate in lipid messenger mediated intracellular signaling? A question revisited

Annexins are physiologically important proteins that play a role in calcium buffering but also influence membrane structure, participate in Ca²⁺-dependent membrane repair events and in remodelling of the cytoskeleton. Thirty years ago several peptides isolated from lung perfusates, peritoneal leukocytes, neutrophiles and renal cells were proven inhibitory to the activity of phospholipase A₂. Those peptides were found to derive from structurally related proteins: annexins AnxA1 and AnxA2. These findings raised the question whether annexins may participate in regulation of the production of lipid second messengers and, therefore, modulate numerous lipid mediated signaling pathways in the cell. Recent advances in the field of annexins made also with the use of knock-out animal models revealed that these proteins are indeed important constituents of specific signaling pathways. In this review we provide evidence supporting the hypothesis that annexins, as membrane-binding proteins and organizers of the membrane lateral heterogeneity, may participate in lipid mediated signaling pathways by affecting the distribution and activity of lipid metabolizing enzymes (most of the reports point to phospholipase A₂) and of protein kinases regulating activity of these enzymes. Moreover, some experimental data suggest that annexins may directly interact with lipid metabolizing enzymes and, in a calcium-dependent or independent manner, with some of their substrates and products. On the basis of these observations, many investigators suggest that annexins are capable of linking Ca²⁺, redox and lipid signaling to coordinate vital cellular responses to the environmental stimuli.

General molecular biology and architecture of nuclear receptors

Nuclear receptors (NRs) regulate and coordinate multiple processes by integrating internal and external signals, thereby maintaining homeostasis in front of nutritional, behavioral and environmental challenges. NRs exhibit strong similarities in their structure and mode of action: by selective transcriptional activation or repression of cognate target genes, which can either be controlled through a direct, DNA binding-dependent mechanism or through crosstalk with other transcriptional regulators, NRs modulate the expression of gene clusters thus achieving coordinated tissue responses. Additionally, non genomic effects of NR ligands appear mediated by ill-defined mechanisms at the plasma membrane. These effects mediate potential therapeutic effects as small lipophilic molecule targets, and many efforts have been put in elucidating their precise mechanism of action and pathophysiological roles. Currently, numerous nuclear receptor ligand analogs are used in therapy or are tested in clinical trials against various diseases such as hypertriglyceridemia, atherosclerosis, diabetes, allergies and cancer and others.

Immunohistochemical localization of Clara cell secretory proteins (CC10-CC26) and Annexin-1 protein in rat major salivary glands

The oral cavity is continuously bathed by saliva secreted by the major and minor salivary glands. Saliva is the first biological medium to confront external materials that are taken into the body as part of food or drink or inhaled volatile substances, and it contributes to the first line of oral defence. In humans, it has been shown that sputum and a variety of biological fluids contain Clara cell secretory proteins (CC10-CC26). Various studies of the respiratory apparatus have suggested their protective effect against inflammatory response and oxidative stress. Recently, CC10 deficiency has been related to the protein Annexin-1 (ANXA1), which has immunomodulatory and anti-inflammatory properties. Considering the defensive role of both Clara cell secretory proteins and ANXA1 in the respiratory apparatus, and the importance of salivary gland secretion in the first line of oral defence, we decided to evaluate the expression of CC10, CC26 and ANXA1 proteins in rat major salivary glands using immunohistochemistry. CC10 expression was found only in the ductal component of the sublingual gland. Parotid and submandibular glands consistently lacked CC10 immunoreactivity. In the parotid gland, both acinar and ductal cells were always CC26-negative, whereas in the submandibular gland, immunostaining was localized in the ductal component and in the periodic acid Schiff (PAS)-positive area. In the sublingual gland, ductal cells were always positive. Acinar cells were not immunostained at all. ANXA1 was expressed in ductal cells in all three major glands. In parotid and sublingual glands, acinar cells were negative. In submandibular glands, immunostaining was present in the mucous PAS-positive portion, whereas serous acinar cells were consistently negative. The existence of some CC10-CC26-ANXA1-positive cells in rat salivary glandular tissue is an interesting preliminary finding which could support the hypothesis, suggested for airway tissue, that these proteins have a defensive and protective role. Protein expression heterogeneity in the different portions of the glands could be an important clue in further investigations of their role.

Glucocorticoid-regulated crosstalk between arachidonic acid and endocannabinoid biochemical pathways coordinates cognitive-, neuroimmune-, and energy homeostasis-related adaptations to stress

Arachidonic acid and its derivatives constitute the major group of signaling molecules involved in the innate immune response and its communication with all cellular and systemic aspects involved on homeostasis maintenance. Glucocorticoids spread throughout the organism their influences over key enzymatic steps of the arachidonic acid biochemical pathways, leading, in the central nervous system, to a shift favoring the synthesis of anti-inflammatory endocannabinoids over proinflammatory metabolites, such as prostaglandins. This shift modifies local immune-inflammatory response and neuronal activity to ultimately coordinate cognitive, behavioral, neuroendocrine, neuroimmune, physiological, and metabolic adjustments to basal and stress conditions. In the hypothalamus, a reciprocal feedback between glucocorticoids and arachidonate-containing molecules provides a mechanism for homeostatic control. This neurochemical switch is susceptible to fine-tuning by neuropeptides, cytokines, and hormones, such as leptin and interleukin-1beta, assuring functional integration between energy homeostasis control and the immune/stress response.

Annexin A1 regulates intestinal mucosal injury, inflammation, and repair

During mucosal inflammation, a complex array of proinflammatory and protective mechanisms regulates inflammation and severity of injury. Secretion of anti-inflammatory mediators is a mechanism that is critical in controlling inflammatory responses and promoting epithelial restitution and barrier recovery. AnxA1 is a potent anti-inflammatory protein that has been implicated to play a critical immune regulatory role in models of inflammation. Although AnxA1 has been shown to be secreted in intestinal mucosal tissues during inflammation, its potential role in modulating the injury/inflammatory response is not understood. In this study, we demonstrate that AnxA1-deficient animals exhibit increased susceptibility to dextran sulfate sodium (DSS)-induced colitis with greater clinical morbidity and histopathologic mucosal injury. Furthermore, impaired recovery following withdrawal of DSS administration was observed in AnxA1 (-/-) animals compared with wild-type (WT) control mice that was independent of inflammatory cell infiltration. Since AnxA1 exerts its anti-inflammatory properties through stimulation of ALX/FPRL-1, we explored the role of this receptor-ligand interaction in regulating DSS-induced colitis. Interestingly, treatment with an ALX/FPRL-1 agonist, 15-epi-lipoxin A4 reversed the enhanced sensitivity of AnxA1 (-/-) mice to DSS colitis. In contrast, 15-epi-lipoxin A4 did not significantly improve the severity of disease in WT animals. Additionally, differential expression of ALX/FPLR-1 in control and DSS-treated WT and AnxA1-deficient animals suggested a potential role for AnxA1 in regulating ALX/FPRL-1 expression under pathophysiological conditions. Together, these results support a role of endogenous AnxA1 in the protective and reparative properties of the intestinal mucosal epithelium.

Increased susceptibility of annexin-A1 null mice to nociceptive pain is indicative of a spinal antinociceptive action of annexin-A1

BACKGROUND AND PURPOSE

Annexin-A1 (ANXA1), a glucocorticoid-regulated protein, mediates several of the anti-inflammatory actions of the glucocorticoids. Previous studies demonstrated that ANXA1 is involved in pain modulation. The current study, using ANXA1 knockout mice (ANXA1-/-), is aimed at addressing the site and mechanism of the modulatory action of ANXA1 as well as possible involvement of ANXA1 in mediating the analgesic action of glucocorticoids.

EXPERIMENTAL APPROACH

The acetic acid-induced writhing response was performed in ANXA1-/- and wild-type (ANXA1+/+) mice with spinal and brain levels of prostaglandin E2 (PGE2) examined in both genotypes. The effect of the ANXA1 peptomimetic Ac2-26 as well as methylprednisolone on the writhing response and on spinal cord PGE2 of ANXA1+/+ and ANXA1-/- was compared. The expression of proteins involved in PGE2 synthesis, cytosolic phospholipase A2 (cPLA2) and cyclooxygenases (COXs), in the spinal cord of ANXA1+/+ and ANXA1-/- was also compared.

KEY RESULTS

ANXA1-/- mice exhibited a significantly greater writhing response and increased spinal cord levels of PGE2 compared with ANXA1+/+ mice. Ac2-26 produced analgesia and reduced spinal PGE2 levels in ANXA1+/+ and ANXA1-/- mice, whereas methylprednisolone reduced the writhing response and spinal PGE2 levels in ANXA1+/+, but not in ANXA1-/- mice. The expression of cPLA2, COX-1, COX-2 and COX-3 in spinal cord tissues was upregulated in ANXA1-/-compared with ANXA1+/+.

CONCLUSIONS AND IMPLICATIONS

We conclude that ANXA1 protein modulates nociceptive processing at the spinal level, by reducing synthesis of PGE2 by modulating cPLA2 and/or COX activity. The analgesic activity of methylprednisolone is mediated by spinal ANXA1.

Glucocorticoids shift arachidonic acid metabolism toward endocannabinoid synthesis: a non-genomic anti-inflammatory switch

Glucocorticoids are capable of exerting both genomic and non-genomic actions in target cells of multiple tissues, including the brain, which trigger an array of electrophysiological, metabolic, secretory and inflammatory regulatory responses. Here, we have attempted to show how glucocorticoids may generate a rapid anti-inflammatory response by promoting arachidonic acid-containing endocannabinoids biosynthesis. According to our hypothesized model, non-genomic action of glucocorticoids results in the global shift of membrane lipid metabolism, subverting metabolic pathways toward the synthesis of the anti-inflammatory endocannabinoids, anandamide (AEA) and 2-arachidonoyl-glycerol (2-AG), and away from arachidonic acid production. Post-transcriptional inhibition of cyclooxygenase-2 (COX(2)) synthesis by glucocorticoids assists this mechanism by suppressing the synthesis of pro-inflammatory prostaglandins as well as endocannabinoid-derived prostanoids. In the central nervous system (CNS) this may represent a major neuroprotective system, which may cross-talk with leptin signaling in the hypothalamus allowing for the coordination between energy homeostasis and the inflammatory response.

Coagulation Activation by Lipopolysaccharides

Lipopolysaccharides at approximate plasma reactivities >3 ng/mL or β-glucans at >0.5-1 μg/mL are toxic for human blood; lipopolysaccharide interacts with membrane components of susceptible cells (eg, monocytes) activating phospholipase A2that destroys the cell membrane. Cell fragments (microparticles or DNA) possess polynegative niches that activate intrinsic hemostasis. Pathologic disseminated intravascular coagulation arises. Blood vessels are obstructed by disseminated thrombi, and vital organ areas become ischemic. Multiorgan failure threatens life of the patient. Diagnosis and therapy of pathologic disseminated intravascular coagulation is of extreme clinical importance. For early diagnosis of pathologic disseminated intravascular coagulation, specific activation markers of coagulation (eg, plasmatic amidolytic thrombin activity) or the plasmatic lipopolysaccharide or glucan reactivity can be measured. A new treatment target might be kallikrein or factor XIIa; 10 to 20 mM arginine is the approximate 50% inhibitory concentration against the contact phase of coagulation. The complex interaction between cell fragments and hemostasis causes pathologic disseminated intravascular coagulation in sepsis.

Gene deletion reveals roles for annexin A1 in the regulation of lipolysis and IL-6 release in epididymal adipose tissue

In this study, epididymal adipose tissue from male annexin 1 (ANXA1)-null and wild-type control mice were used to explore the potential role of ANXA1 in adipocyte biology. ANXA1 was detected by Western blot analysis in wild-type tissue and localized predominantly to the stromal-vascular compartment. Epididymal fat pad mass was reduced by ANXA1 gene deletion, but adipocyte size was unchanged, suggesting that ANXA1 is required for the maintenance of adipocyte and/or preadipocyte cell number. Epididymal tissue from wild-type mice responded in vitro to noradrenaline and isoprenaline with increased glycerol release, reduced IL-6 release, and increased cAMP accumulation. Qualitatively similar but significantly attenuated responses to the catecholamines were observed in tissue from ANXA1-null mice, an effect that was not associated with changes in beta-adrenoceptor mRNA expression. Lipopolysaccharide (LPS) also stimulated lipolysis in vitro, but its effects were muted by ANXA1 gene deletion. By contrast, LPS failed to influence IL-6 release from wild-type tissue but stimulated the release of the cytokine from tissue from ANXA1-null mice. ANXA1 gene deletion did not affect glucocorticoid receptor expression or the ability of dexamethasone to suppress catecholamine-induced lipolysis. It did, however, augment IL-6 expression and modify the inhibitory effects of glucocorticoids on IL-6 release. Collectively, these studies suggest that ANXA1 supports aspects of adipose tissue mass and alters the sensitivity of epididymal adipose tissue to catecholamines, glucocorticoids, and LPS, thereby modulating lipolysis and IL-6 release.

Annexin I regulates SKCO-15 cell invasion by signaling through formyl peptide receptors

Annexin 1 (AnxA1) is a multifunctional phospholipid-binding protein associated with the development of metastasis in some invasive epithelial malignancies. However, the role of AnxA1 in the migration/invasion of epithelial cells is not known. In this study, experiments were performed to investigate the role of AnxA1 in the invasion of a model epithelial cell line, SKCO-15, derived from colorectal adenocarcinoma. Small interfering RNA-mediated knockdown of AnxA1 expression resulted in a significant reduction in invasion through Matrigel-coated filters. Localization studies revealed a translocation of AnxA1 to the cell surface upon the induction of cell migration, and functional inhibition of cell surface AnxA1 using antiserum (LCO1) significantly reduced cell invasion. Conversely, SKCO-15 cell invasion was increased by approximately 2-fold in the presence of recombinant full-length AnxA1 and the AnxA1 N-terminal-derived peptide mimetic, Ac2-26. Because extracellular AnxA1 has been shown to regulate leukocyte migratory events through interactions with n-formyl peptide receptors (nFPRs), we examined the expression of FPR-1, FPRL-1, and FPRL-2 in SKCO-15 cells by reverse transcriptase-PCR and identified expression of all three receptors in this cell line. Treatment of SKCO-15 cells with AnxA1, Ac2-26, and the classical nFPR agonist, formylmethionylleucylphenylalanine, induced intracellular calcium release consistent with nFPR activation. Furthermore, the nFPR antagonist, Boc2, abrogated the AnxA1 and Ac2-26-induced intracellular calcium release and increase in SKCO-15 cell invasion. Together, these results support an autocrine/paracrine role for membrane AnxA1 in stimulating SKCO-15 cell migration through nFPR activation. The findings in this study suggest that activation of nFPRs stimulates epithelial cell motility important in the development of metastasis as well as wound healing.

Non-genomic glucocorticoid effects to provide the basis for new drug developments

Glucocorticoids act via genomic and non-genomic actions. The genomic glucocorticoid actions are well known and new details on processes of transactivation and transrepression have been reported recently. Here we describe the current knowledge on non-genomic glucocorticoid actions and discuss why these actions are considered to be of therapeutic relevance. It is assumed that rapid non-genomic glucocorticoid effects are mediated by three different mechanisms: (1) physicochemical interactions with cellular membranes (non-specific non-genomic effects); (2) membrane-bound glucocorticoid receptor (mGCR)-mediated non-genomic effects; and (3) cytosolic glucocorticoid receptor (cGCR)-mediated non-genomic effects. With regard to the first mechanism, we discuss here lazaroids and the novel development of drug targeting with liposomes as the carrier system for glucocorticoids. The clinical use of the latter two mechanisms is still speculative, but intriguing ideas are being discussed in this regard.

Annexin A8 is up-regulated during mouse mammary gland involution and predicts poor survival in breast cancer

PURPOSE

Microarray studies have linked Annexin A8 RNA expression to a "basal cell-like" subset of breast cancers, including BRCA1-related cancers, that are characterized by cytokeratin 5 (CK5) and CK17 expression and show poor prognosis. We assessed Annexin A8's contribution to the overall prognosis and its expression in normal, benign, and cancerous tissue and addressed Annexin A8's physiologic role in the mammary gland.

EXPERIMENTAL DESIGN

Using microarrays and reverse transcription-PCR, the Annexin A8 expression was studied during mouse mammary gland development and in isolated mammary structures. Reverse transcription-PCR on cultured human luminal and basal cells, along with immunocytochemistry on normal and benign breast tissues, was used for cellular localization. Annexin A8's prognostic relevance and its coexpression with CK5 were assessed on tissue arrays of 1,631 cases of invasive breast cancer. Coexpression was further evaluated on a small cohort of 14 BRCA1-related breast cancers.

RESULTS

Annexin A8 was up-regulated during mouse mammary gland involution and in pubertal ductal epithelium. Annexin A8 showed preferred expression in cultured basal cells but predominant luminal expression in normal human breast tissue in vivo. Hyperplasias and in situ carcinomas showed a strong staining of basal cells. Annexin A8 expression was significantly associated with grade (P < 0.0001), CK5 (P < 0.0001), and estrogen receptor status (P < 0.0001); 85.7% BRCA1-related breast tumors coexpressed Annexin A8 and CK5.

CONCLUSION

Annexin A8 is involved in mouse mammary gland involution. In humans, it is a luminally expressed protein with basal expression in cell culture and in hyperplasia/ductal carcinoma in situ. Expression in invasive breast carcinomas has a significant effect on survival (P = 0.03) but is not independent of grade or CK5.

Annexin 1 is secreted in situ during ulcerative colitis in humans

Although annexin l exerts extracellular anti-inflammatory properties, little is known about its release in inflammatory diseases. Here, we characterized annexin 1 secretion in ulcerative colitis (UC) patients. Annexin 1 was detected by immunoblotting, in tissue homogenates and supernatants of colonic biopsies incubated in culture media, and in luminal colonic perfusates of UC patients. Annexin 1 was released by inflamed colonic biopsies from patients having severe UC but not by biopsies from healthy colon of the same patient or by biopsies from non-UC patients or from patients with slight or moderate UC. Annexin 1 was detected in luminal colonic perfusates of patients having moderate or slight UC but not in perfusates from control patients. The level of annexin 1 expression and secretion was unrelated to long-term glucocorticoid treatment, but annexin 1 secretion in perfusates was induced, in some patients, by short-term glucocorticoid exposure. These results show that annexin 1 is secreted endogenously in the colon of patients with UC. This secretion, which occurs both in vitro and in vivo, depends on the severity of inflammation. Given the anti-inflammatory effects of annexin 1, this protein may serve to down-regulate the inflammatory response in the course of inflammatory bowel disease.

Kinase-dependent regulation of the secretion of thyrotrophin and luteinizing hormone by glucocorticoids and annexin 1 peptides

Our previous studies have identified a role for annexin 1 (ANXA1), a protein produced by the pituitary folliculostellate cells, as a paracrine/juxtacrine mediator of the acute regulatory effects of glucocorticoids on the release of adrenocorticotropic hormone and other pituitary hormones. In the present study, we focused on the secretion of thyroid stimulating hormone (TSH) and luteinizing hormone (LH) and used a battery of ANXA1-derived peptides to identify the key domains in the ANXA1 molecule that are critical to the inhibition of peptide release. In addition, as ANXA1 is a substrate for protein kinase C (PKC) and tyrosine kinase, we examined the roles of these kinases in the manifestation of the ANXA1-dependent inhibitory actions of dexamethasone on TSH and LH release. Dexamethasone suppressed the forskolin-induced release of TSH and LH from rat anterior pituitary tissue in vitro. Its effects were mimicked by human recombinant ANXA1 (hrANXA1) and a truncated protein, ANXA1(1-188). ANXA1(Ac2-26), also suppressed stimulated peptide release but it lacked both the potency and the efficacy of the parent protein. Shorter N-terminal ANXA1 sequences were without effect. The PKC inhibitor PKC(19-36) abolished the inhibitory actions of dexamethasone on the forskolin-evoked release of TSH and LH; it also attenuated the inhibitory actions of ANXA1(Ac2-26). Similar effects were produced by annexin 5 (ANXA5) which sequesters PKC in other systems. By contrast, the tyrosine kinase inhibitors, p60v-src (137-157) and genistein, had no effect on the secretion of TSH or LH alone or in the presence of forskolin and/or dexamethasone. Dexamethasone caused the translocation of a tyrosine-phosphorylated species of ANXA1 to the surface of pituitary cells. The total amount of ANXA1 exported from the cells in response to the steroid was unaffected by tyrosine kinase blockade. However, the degree of tyrosine-phosphorylation of the exported protein was markedly reduced by genistein. These results suggest that (i) the ANXA1-dependent inhibitory actions of dexamethasone on the release of TSH and LH require PKC and sequences in the N-terminal domain of ANXA1, but are independent of tyrosine kinase, and (ii) while dexamethasone induces the cellular exportation of a tyrosine-phosphorylated species of ANXA1, tyrosine phosphorylation per se is not critical to the steroid-induced passage of ANXA1 across the membrane.

Translocation of annexin I from cellular membrane to the nuclear membrane in human esophageal squamous cell carcinoma

AIM: To investigate the alteration of the annexin I subcellular localization in esophageal squamous cell carcinoma (ESCC) and the correlation between the translocation and the tumorigenesis of ESCC.

METHODS: The protein localization of annexin I was detected in both human ESCC tissues and cell line via the indirect immunofluorescence strategy.

RESULTS: In the normal esophageal epithelia the annexin I was mainly located on the plasma membrane and formed a consecutive typical trammels net. Annexin I protein also expressed dispersively in cytoplasm and the nuclei without specific localization on the nuclear membrane. In esophageal cancer annexin I decreased very sharply with scattered disappearance on the cellular membrane, however it translocated and highly expressed on the nuclear membrane, which was never found in normal esophageal epithelia. In cultured esophageal cancer cell line annexin I protein was also focused on the nuclear membrane, which was consistent with the result from esophageal cancer tissues.

CONCLUSION: This observation suggests that the translocation of annexin I protein in ESCC may correlate with the tumorigenesis of the esophageal cancer.

Evidence for a role of the adenosine 5'-triphosphate-binding cassette transporter A1 in the externalization of annexin I from pituitary folliculo-stellate cells

Annexin 1 (ANXA1) has a well-demonstrated role in early delayed inhibitory feedback of glucocorticoids in the pituitary. ANXA1 is located in folliculo-stellate (FS) cells, and glucocorticoids act on these cells to externalize and stimulate the synthesis of ANXA1. However, ANXA1 lacks a signal sequence so the mechanism by which ANXA1 is externalized from FS cells was unknown and has been investigated. The ATP-binding cassette (ABC) transporters are a large group of transporters with varied roles that include the externalization of proteins. Glucocorticoid-induced externalization of ANXA1 from an FS cell line (TtT/GF) and rat anterior pituitary was blocked by glyburide, which inhibits ABC transporters. Glyburide also blocked the glucocorticoid inhibition of forskolin-stimulated ACTH release from pituitary tissue in vitro. RT-PCR revealed mRNA and Western blotting demonstrated protein for the ATP binding cassette A1 (ABCA1) transporter in mouse FS, TtT/GF, and A549 lung adenocarcinoma cells from which glucocorticoids also induce externalization of ANXA1. In TtT/GF cells, immunofluorescence labeling revealed a near total colocalization of cell surface ANXA1 and ABCA1. We conclude that ANXA1, which mediates the early delayed feedback of glucocorticoids in the anterior pituitary, is externalized from FS cells by an ABC transporter and that the ABCA1 transporter is a likely candidate.

Nuclear localisation of cytosolic phospholipase A2-alpha in the EA.hy.926 human endothelial cell line is proliferation dependent and modulated by phosphorylation

Cytosolic phospholipase A(2)-alpha (cPLA(2)-alpha) is a calcium-sensitive enzyme involved in receptor-mediated eicosanoid production. In resting cells, cPLA(2)-alpha is present in the cytosol and nucleus and translocates to membranes via its calcium-dependent lipid-binding (CaLB) domain following stimulation. cPLA(2)-alpha is also regulated by phosphorylation on several residues, which results in enhanced arachidonic acid release. Little is known about the factors controlling the nuclear localisation of cPLA(2)-alpha. Here the nuclear localisation of cPLA(2)-alpha in the EA.hy.926 human endothelial cell line was investigated. Nuclear localisation was dependent on proliferation, with subconfluent cells containing higher levels of nuclear cPLA(2)-alpha than contact-inhibited confluent or serum-starved cells. The broad-range protein kinase inhibitor staurosporine caused a decrease in the nuclear level of cPLA(2)-alpha, whereas the protein phosphatase inhibitor okadaic acid increased the level of nuclear cPLA(2)-alpha. Using inhibitors for specific mitogen-activated protein (MAP) kinases, both p42/44(MAPK) and p38(MAPK) were shown to be important in modulating nuclear localisation. Finally, inhibition of nuclear import and export using Agaricus bisporus lectin and leptomycin B, respectively, demonstrated that cPLA(2)-alpha contains functional nuclear localisation and export signals. Thus we have identified a novel mode of regulation of cPLA(2)-alpha. This, together with the increasing body of evidence supporting the role of nuclear lipid second messengers in gene expression and proliferation, may have important implications for controlling the growth of endothelial cells in angiogenesis and tumour progression.

Different glucocorticoids vary in their genomic and non-genomic mechanism of action in A549 cells

We have examined the effects of 12 glucocorticoids as inhibitors of A549 cell growth. Other than cortisone and prednisone, all the glucocorticoids inhibited cell growth and this was strongly correlated (r=0.91) with inhibition of prostaglandin (PG)E(2) formation. The molecular mechanism by which the active steroids prevented PGE(2) synthesis was examined and three groups were identified. Group A drugs did not inhibit arachidonic acid release but inhibited the induction of COX2. Group B drugs were not able to inhibit the induction of COX2 but inhibited arachidonic acid release through suppression of cPLA(2) activation. Group C drugs were apparently able to bring about both effects. The inhibitory actions of all steroids was dependent upon glucocorticoid receptor occupation since RU486 reversed their effects. However, group A acted through the NF-kappaB pathway to inhibit COX2 as the response was blocked by the inhibitor geldanamycin which prevents dissociation of GR and the effect was blocked by APDC, the NF-kappaB inhibitor. On the other hand, the group B drugs were not inhibited by NF-kappaB inhibitors or geldanamycin but their effect was abolished by the src inhibitor PP2. Group C drugs depended on both pathways. In terms of PGE(2) generation, there is clear evidence of two entirely separate mechanisms of glucocorticoid action, one of which correlates with NF-kappaB mediated genomic actions whilst the other, depends upon rapid effects on a cell signalling system which does not require dissociation of GR. The implications for these findings are discussed.

Investigation into the involvement of phospholipases A(2) and MAP kinases in modulation of AA release and cell growth in A549 cells

1. We have investigated the contribution of specific PLA(2)s to eicosanoid release from A549 cells by using specific inhibitors of secretory PLA(2) (ONO-RS-82 and oleyloxyethylphosphocholine), cytosolic PLA(2) (AACOCF(3) and MAFP) and calcium-independent PLA(2) (HELSS, MAFP and PACOCF(3)). Similarly, by using specific inhibitors of p38 MAPK (SB 203580), ERK1/2 MAPK (Apigenin) and MEK1/2 (PD 98059) we have further evaluated potential pathways of AA release in this cell line. 2. ONO-RS-82 and oleyloxyethylphosphocholine had no significant effect on EGF or IL-1beta stimulated (3)H-AA or PGE(2) release or cell proliferation. AACOCF(3), HELSS, MAFP and PACOCF(3) significantly inhibited both EGF and IL-1beta stimulated (3)H-AA and PGE(2) release as well as cell proliferation. Apigenin and PD 98509 significantly inhibited both EGF and IL-1beta stimulated (3)H-AA and PGE(2) release and cell proliferation whereas, SB 203580 had no significant effect on EGF or IL-1beta stimulated (3)H-AA release, or cell proliferation but significantly suppressed EGF or IL-1beta stimulated PGE(2) release. 3. These results confirm that the liberation of AA release, generation of PGE(2) and cell proliferation is mediated largely through the actions of cPLA(2) whereas, sPLA(2) plays no significant role. We now also report a hitherto unsuspected contribution of iPLA(2) to this process and demonstrate that the stimulating action of EGF and IL-1beta in AA release and cell proliferation is mediated in part via a MEK and ERK-dependent pathway (but not through p38MAPK). We therefore propose that selective inhibitors of MEK and MAPK pathways may be useful in controlling AA release, eicosanoid production and cell proliferation.

The MAP kinase inhibitors, PD098059, UO126 and SB203580, inhibit IL-1beta-dependent PGE(2) release via mechanistically distinct processes

1. In common with human bronchial epithelial cells, pulmonary A549 cells release prostaglandin (PG) E(2) in response to pro-inflammatory cytokines. We have therefore used these cells to examine the effect of the selective mitogen activated protein (MAP) kinase inhibitors; PD098059, a mitogen activated and extracellular regulated kinase kinase (MEK) 1 inhibitor, UO126, a dual MEK1 & MEK2 inhibitor, and SB203580, a p38 MAP kinase inhibitor in the IL-1beta-dependent release of PGE(2). 2. Following IL-1beta treatment the extracellular regulated kinases (ERKs) and the p38 MAP kinases were rapidly phosphorylated. 3. PD09059, UO126 and SB203580 prevented IL-1beta-induced PGE(2) release at doses that correlated closely with published IC(50) values. Small or partial effects at the relevant doses were observed on induction of cyclo-oxygenase (COX) activity or COX-2 protein suggesting that the primary effects were at the level of arachidonate availability. 4. Neither PD098059 nor SB203580 showed any effect on IL-1beta-induced arachidonate release. We therefore speculate that the MEK1/ERK and p38 kinase cascades play a role in the functional coupling of arachidonate release to COX-2. 5. In contrast, UO126 was highly effective at inhibiting IL-1beta-dependent arachidonate release, implicating MEK2 in the activation of the PLA(2) that is involved in IL-1beta-dependent PGE(2) release. 6. We conclude that the MEK1, MEK2 and p38 MAP kinase inhibitors, PD098059, UO126 and SB203580, are highly potent in respect of inflammatory PG release. Finally, we conclude that these inhibitors act via mechanistically distinct processes, which may have anti-inflammatory benefits.

Glucocorticoids act within minutes to inhibit recruitment of signalling factors to activated EGF receptors through a receptor-dependent, transcription-independent mechanism

Recruitment to activated tyrosine kinase growth factor receptors of Grb2 and p21(ras) leads to downstream activation of the kinases Raf, MAPK/Erk kinase (Mek) and, subsequently, extracellular signal-regulated kinase (Erk). Activated Erk phosphorylates specific serine residues within cytosolic phospholipase A(2) (PLA(2)), promoting enzyme translocation to membranes and facilitating liberation of arachidonic acid (AA). In the A549 human adenocarcinoma cell line dexamethasone inhibited epidermal growth factor (EGF)-stimulated cytosolic PLA(2) (cPLA(2)) activation and AA release by blocking the recruitment of Grb2 to the activated EGF receptor (EGF-R) through a glucocorticoid receptor (GR)-dependent (RU486-sensitive), transcription-independent (actinomycin-insensitive), mechanism. The dexamethasone-induced block of Grb2 recruitment was parallelled by changes in phosphorylation status and subcellular localization of lipocortin 1 (LC1) and an increase in the amount of the tyrosine phosphoprotein co-localized with EGF-R. Like dexamethasone, peptides containing E-Q-E-Y-V from the N-terminal domain of LC1 also blocked ligand-induced association of Grb2, p21(ras) and Raf. Our results point to an unsuspected rapid effect of glucocorticoids, mediated by occupation of GR but not by changes in gene transcription, which is brought about by competition between LC1 and Grb2 leading to a failure of recruitment off signalling factors to EGF-R

Increased apoptosis in U937 cells over-expressing lipocortin 1 (annexin I)

The potential involvement of endogenous lipocortin 1 in the process of cellular apoptosis, particularly in cells of the myelo-monocytic lineage, has been investigated. U937 cells were transfected either with an antisense or a sense DNA for lipocortin 1 and the stable clones 36.4AS clone (20-40% lower lipocortin 1 levels) and 15S (30% higher lipocortin 1 levels) were obtained. Cell apoptosis was induced by incubation with tumor necrosis factor-alpha: optimal responses were observed within a 24 h incubation period at a 5 ng/ml concentration. Apoptosis was assessed both morphologically, by annexin V binding and cell cycle analysis with propidium iodide. Whilst no consistent difference was seen between wild type cells and clone 36.4AS, a higher incidence of apoptosis (ranging from +30% to + 60%) was observed in the 15S clone. Release of arachidonic acid from loaded cells was promoted by 24 h incubation with the cytokine, and a higher degree of release was measured in the 15S clone. These data indicate that endogenous intracellular lipocortin 1 is involved in the promotion of apoptosis in cells of the myelo-monocytic derivation.

The regulation of prostaglandin output from term intact fetal membranes by anti-inflammatory cytokines

Prostaglandins are some of the main mediators which control parturition, and their production by intrauterine tissues can be up-regulated by pro-inflammatory cytokines. Anti-inflammatory cytokines may oppose these effects, and in this study we have investigated how two such cytokines affected fetal membrane function. Interleukin-10 (IL-10) inhibited the output of prostaglandin E2 (PGE2) from intact fetal membranes under basal and lipopolysaccharide (LPS)-stimulated conditions, and there was a parallel decrease in the expression of mRNA for COX-2. IL-10 also inhibited the production of interleukin-1beta (IL-1beta) and the expression of mRNA for IL-1beta, indicating that this cytokine has a broad anti-inflammatory effect. Transforming growth factor-beta1 (TGF-beta1), which is generally considered to be anti-inflammatory had opposite effects on PGE2 production, in that it increased the output of PGE2 for up to 8 hr. TGF-beta1 increased levels of type-2 cyclo-oxygenase (COX-2) and cytosolic phospholipase A2 (cPLA2) protein, and also activated the cPLA2 enzyme present; the profile of effects is similar to that of the pro-inflammatory cytokine IL-1beta, and was not expected. Combinations of TGF-beta1 with IL-1beta also increased PGE2 output and caused appropriate changes in prostaglandin pathway enzymes, whereas TGF-beta1 and IL-1alpha had more limited effects. Further studies are needed to establish the physiological significance of these findings, but TGF-beta1 does not seem to act as an inhibitory cytokine in intact fetal membranes at term.

Regulatory effects of HDL on smooth muscle cell prostacyclin release

One mechanism by which high density lipoproteins (HDLs) exert their protective effect against coronary artery disease could be related to the induction of prostacyclin (PGI(2)) release in the vessel wall. We have recently shown that HDL increases PGI(2) production in rabbit smooth muscle cells (RSMCs) and that this increase is dependent on cyclooxygenase-2 (Cox-2). Here we analyze the mechanism by which rabbit HDL induces PGI(2) release in RSMCs. Our results show that although HDL(2) and HDL(3) share a similar capacity to induce Cox-2 protein levels, HDL(3) stimulates a higher PGI(2) release than does HDL(2), probably because of their relative arachidonate contents. Acetylsalicylic acid pretreatment (300 micromol/L, 30 minutes) significantly reduced the HDL-induced PGI(2) release, suggesting that both preexisting and induced Cox-2 activities were involved in the HDL effect. Ca(2+)-dependent cytosolic phospholipase A(2) (cPLA(2)) and Cox-1 protein levels were not altered by HDL. Dexamethasone (2 micromol/L), which also inhibited the HDL-induced PGI(2) release, reduced significantly both Cox-2 mRNA and protein levels without affecting cPLA(2) and Cox-1 protein levels. In addition, methylarachidonyl fluorophosphonate, a potent inhibitor of cPLA(2), did not produce any effect on HDL-induced PGI(2) release. In the presence of cycloheximide, Cox-2 mRNA levels were induced by HDL and inhibited by dexamethasone, suggesting that HDL and dexamethasone work in the absence of de novo protein synthesis. These results indicate an early effect of HDL on PGI(2) biosynthesis, specifically increasing Cox-2. PD98059, an inhibitor of mitogen-activated protein kinase kinase, completely inhibited HDL-induced PGI(2) release, whereas GF109203X, a protein kinase C inhibitor, had no effect. Thus, HDL induces PGI(2) synthesis by a mechanism dependent on the mitogen-activated protein kinase pathway but independent of protein kinase C.

Effects of topical corticosteroids on inflammatory mediator-induced eicosanoid release by human airway epithelial cells

BACKGROUND

Airway epithelial cells are among the first cells to come in contact with aerosolized corticosteroids. However, the relative potencies and time course of action of the several commonly used aerosolized corticosteroids on eicosanoid production by airway epithelial cells are unknown.

OBJECTIVES

This study compared the effects of fluticasone, budesonide, and triamcinolone on eicosanoid output by human airway epithelial cells in vitro. We also determined the spectrum of eicosanoids affected and the mechanism for corticosteroid action.

METHODS

Cultured BEAS-2B airway epithelial cells (a transformed cell line) were exposed to corticosteroids (1 nmol/L to 1 micromol/L) for 2 to 48 hours and then assayed for basal- and bradykinin (BK)-stimulated eicosanoid output. The eicosanoid profile was identified by HPLC in tritiated arachidonic acid prelabelled cells, and PGE2, the major eicosanoid product, was quantitated by RIA. The effect of corticosteroids on the immunoreactivity of key proteins involved in eicosanoid metabolism (ie, cyclooxygenase [COX], phospholipase A2 [PLA2], and Clara cell protein, a PLA2 inhibitor) was determined by Western blotting.

RESULTS

Eicosanoid output was largely confined to prostaglandins with values of 5 +/- 2 and 82 +/- 35 ng PGE2/10(6) cells for basal- and BK stimulation, respectively (n = 8). All 3 corticosteroids inhibited basal- and BK-induced PGE2 output in a dose- and time-dependent manner. Fluticasone and budesonide completely eliminated PGE2 output in nanomolar concentrations in contrast to triamcinolone, which required micromolar concentration. The rank order of potency was: fluticasone = budesonide > triamcinolone. The time course of action for PGE2 inhibition also differed, with budesonide acting more slowly than the other 2 corticosteroids (P = .04). All 3 corticosteroids markedly reduced COX2 with little effect on COX1, cPLA2 (Type IV), or iPLA2 (Type VI) immunoreactivity or their relative distribution in cytosol versus membrane fractions. Clara cell protein immunoreactivity was undetectable in control and corticosteroid-treated cell lysates.

CONCLUSION

These results show that in a human airway epithelial cell line, the 3 inhaled corticosteroids commonly used to treat asthma differ in onsets of action as inhibitors of prostaglandin synthesis and vary considerably in potency. All 3 corticosteroids act mechanistically in similar fashion by inhibiting COX2 synthesis.

Neutrophil elastase increases MUC5AC mRNA and protein expression in respiratory epithelial cells

Chronic neutrophil-predominant inflammation and hypersecretion of mucus are common pathophysiological features of cystic fibrosis, chronic bronchitis, and viral- or pollution-triggered asthma. Neutrophils release elastase, a serine protease, that causes increased mucin production and secretion. The molecular mechanisms of elastase-induced mucin production are unknown. We hypothesized that as part of this mechanism, elastase upregulates expression of a major respiratory mucin gene, MUC5AC. A549, a human lung carcinoma cell line that expresses MUC5AC mRNA and protein, and normal human bronchial epithelial cells in an air-liquid interface culture were stimulated with neutrophil elastase. Neutrophil elastase increased MUC5AC mRNA levels in a time-dependent manner in both cell culture systems. Neutrophil elastase treatment also increased MUC5AC protein levels in A549 cells. The mechanism of MUC5AC gene regulation by elastase was determined in A549 cells. The induction of MUC5AC gene expression required serine protease activity; other classes of proteases had no effect on MUC5AC gene expression. Neutrophil elastase increased MUC5AC mRNA levels by enhancing mRNA stability. This is the first report of mucin gene regulation by this mechanism.

Respiratory carcinoma cell lines. MUC genes and glycoconjugates

Lung carcinoma cell lines are being used in many laboratories to study various airway epithelial functions, including mucin gene expression. To identify model systems for investigating regulation of MUC5/5AC gene expression and secretion of MUC5/5AC mucins in airway epithelial cells, we evaluated the expression of several mucin genes in six carcinoma cell lines of respiratory tract origin. RNA was extracted from A549, Calu-3, NCI H292, Calu-6, RPMI 2650, and A-427 cells; MUC1, MUC2, MUC4, MUC5/5AC, and MUC5B messenger RNA (mRNA) expression was determined. By Northern analyses, all cell lines expressed MUC1 mRNA, whereas MUC2 mRNA was not detectable in any of the cell lines. RPMI 2650 cell lines expressed only MUC1 mRNA. NCI-H292 cells expressed MUC4 and low levels of MUC5/5AC mRNA. Calu-3 and A549 cells expressed MUC5/5AC mRNA; A549 cells also expressed MUC5B mRNA. Glycoconjugates secreted by lung carcinoma cells were also examined. By wheat germ lectin analysis, Calu-3, H292, and A549 cells secreted high molecular weight glycoproteins having N-acetylglucosamine and/or sialic acid moieties. Western blot analyses with an anti-MUC5:TR-3A antibody demonstrated that Calu-3 and A549 cells secreted MUC5/5AC mucins. All six carcinoma cell lines secreted large, radiolabeled, sulfated macromolecules; the majority were proteoglycans that were digested by hyaluronidase. However, Calu-3 cells also secreted sulfated high molecular-weight glycoproteins that were immunoprecipitated by anti-MUC5:TR-3A antibody. These studies demonstrated that Calu-3 and A549 cell lines expressed high and moderate amounts of MUC5/5AC mRNA and MUC5/5AC mucins, whereas H292 cells expressed lesser amounts. These cell lines should prove useful for studies of MUC5/5AC gene expression and MUC5/5AC biosynthesis, trafficking, and secretions in airway epithelial cells.

Lung type II cell and macrophage annexin I release: differential effects of two glucocorticoids

Annexin I (lipocortin 1) is abundant in lung secretions. Concentrations rise after oral glucocorticoid, but the effect of inhaled budesonide on annexin I release is unknown. Extracellular annexin I in bronchoalveolar lavage fluid (BALF) from 11 asthmatic patients was unaffected by inhaled budesonide (800 microgramgs twice daily for 4 wk; mean after budesonide, 110 ng/mg albumin; after placebo, 107 ng/mg albumin). Rat alveolar macrophages (AMs) and alveolar epithelial type II (ATII) cells were cultured alone and with budesonide or dexamethasone. Mean basal concentrations of cellular (3.5 ng/10(6) AMs; 4.4 ng/10(6) ATII cells) and secreted (1. 4 ng/10(6) AMs; 1.8 ng/10(6) ATII cells) annexin I were similar in AMs and ATII cells. Although budesonide subdued annexin I secretion from both cell types, dexamethasone stimulated annexin I release. Annexin I release from ATII cells peaked at 10(-7) M dexamethasone but at 10(-3) M dexamethasone from AMs. Thus, at low concentrations of dexamethasone, ATII cells probably contribute more annexin I to respiratory tract secretions than AMs, although at high concentrations, both cells probably contribute. The study demonstrates previously undescribed differences between glucocorticoids and between AMs and ATII cells with respect to annexin I regulation.

Annexin I is a local mediator in neural-endocrine feedback control of inflammation

Annexin I is a local mediator in neural-endocrine feedback control of inflammation. J. Neurophysiol. 80: 3120-3126, 1998. Activation of primary afferent nociceptors induces a neural endocrine-mediated inhibition of the inflammatory response via a circuit that includes ascending spinal pathways and activation of the hypothalamic-pituitary adrenal (HPA) axis. This circuit inhibits sympathetic neuron-dependent plasma extravasation (PE) in the rat knee joint produced by bradykinin (BK), but not sympathetic neuron-independent PE produced by platelet activating factor (PAF). Noxious (25 mA) but not non-noxious (2.5 mA) electrical stimulation significantly increased plasma corticosterone concentrations, and intravenous infusion of corticosterone (5 micrograms/min) mimicked inhibition of BK-induced PE produced by noxious stimulation. However, perfusion of corticosterone locally through the knee joint, at doses that do not have a systemic action (i.e., </=1 microM), did not inhibit BK-induced PE. Annexin I (lipocortin-1), a 37-kDa member of a family of phospholipid and calcium binding proteins, can mediate local anti-inflammatory effects of glucocorticoids via a mechanism that is partially dependent on inhibition of phospholipase A2 activity and adhesion and transmigration of polymorphonuclear leukocytes. Because BK-induced PE is dependent on both polymorphonuclear leukocytes and phospholipase A2 activity, we tested the hypothesis that the action of corticosterone to inhibit BK-induced PE is mediated by stimulating the production and release of annexin I. Perfusion of BK (150 nM) through the rat knee joint induces a rapid and sustained increase in PE. Co-perfusion of BK with annexin I (100 ng/ml) through the knee joint mimics the inhibition of BK-induced PE produced by noxious electrical stimulation or by intravenous corticosterone. Co-perfusion of BK with annexin I antibody (LCPS1, 1:60 dilution) prevented the inhibition of BK-induced PE produced by noxious electrical stimulation or intravenous corticosterone adminstration. PAF-induced PE, which is not dependent on polymorphonuclear leukocytes, was not inhibited by local perfusion of annexin I. These data suggest that the inhibitory effect of C-fiber activity on BK-induced PE, acting via an HPA circuit, is mediated by annexin I in the knee joint.

Cellular gene expression altered by human cytomegalovirus: global monitoring with oligonucleotide arrays

Mechanistic insights to viral replication and pathogenesis generally have come from the analysis of viral gene products, either by studying their biochemical activities and interactions individually or by creating mutant viruses and analyzing their phenotype. Now it is possible to identify and catalog the host cell genes whose mRNA levels change in response to a pathogen. We have used DNA array technology to monitor the level of approximately 6,600 human mRNAs in uninfected as compared with human cytomegalovirus-infected cells. The level of 258 mRNAs changed by a factor of 4 or more before the onset of viral DNA replication. Several of these mRNAs encode gene products that might play key roles in virus-induced pathogenesis, identifying them as intriguing targets for further study.

Increased expression of annexin I and thioredoxin detected by two-dimensional gel electrophoresis of drug resistant human stomach cancer cells

The therapy of advanced cancer using chemotherapy alone or in combination with radiation or hyperthermia yields an overall response rate of about 20-50%. This success is often marred by the development of resistance to cytostatic drugs. Our aim was to study the global analysis of protein expression in the development of chemoresistance in vitro. We therefore used a cell culture model derived from the gastric carcinoma cell line EPG 85-257P. A classical multidrug-resistant subline EPG85-257RDB selected to daunorubicin and an atypical multidrug-resistant cell variant EPG85-257RNOV selected to mitoxantrone, were analysed using two-dimensional electrophoresis in immobilized pH-gradients (pH 4.0-8.0) in the first dimension and linear polyacrylamide gels (12%) in the second dimension. After staining with coomassie brilliant blue, image analysis was performed using the PDQuest system. Spots of interest were isolated using preparative two-dimensional electrophoresis and subjected to microsequencing. A total of 241 spots from the EPG85-257RDB-standard and 289 spots from the EPG85-257RNOV-standard could be matched to the EPG85-257P-standard. Microsequencing after enzymatic hydrolysis in gel, mass spectrometric data and sequencing of the peptides after their fractionation using microbore HPLC identified that two proteins annexin I and thioredoxin were overexpressed in chemoresistant cell lines. Annexin I was present in both the classical and the atypical multidrug-resistant cells. Thioredoxin was found to be overexpressed only in the atypical multidrug-resistant cell line.

Activation of phospholipase D signaling pathway by epidermal growth factor in osteoblastic cells

The receptor-mediated activation of phospholipase D (PLD) is a major signaling pathway in several cell systems. This study determined the effects of epidermal growth factor (EGF) on PLD activity in normal rat osteoblastic cells. Primary cultures were obtained from fetal rat calvaria by sequential collagenase digestion and seeded in BGJb media supplemented with 10% fetal calf serum. PLD activity was assayed by the transphosphatidylation reaction in [H3]myristic acid (5 microCi/ml)-labeled cells treated with EGF in the presence of 5% ethanol and measuring the production of phosphatidylethanol (PEtOH). Lipids were extracted and separated by thin-layer chromatography, detected by iodine staining, and the areas of interest were scraped off and transferred to vials for scintillation counting. EGF significantly increased PEtOH production in a dose-dependent manner and at short (10-60 s) and long (up to 30 minutes) incubation periods (p < 0.05). Phosphatidic acid levels were also significantly increased (p < 0.05) compared with unstimulated controls, but the levels were approximately 60% less than those of PEtOH. 4b-phorbol 12-myristate, 13-acetate (PMA) also produced a significant increase in PEtOH levels when compared with unstimulated control cultures, but when PMA was added together with EGF, the production of PEtOH was reduced about 30%. Pretreatment of cells with the protein kinase C (PKC) inhibitor H-7 caused a significant increase in PEtOH levels, compared with cells stimulated with EGF alone. Preincubation of cells with pertussis toxin produced a partial decrease in PEtOH levels. This study demonstrates that EGF activates the PLD signaling cascade in normal rat osteoblastic cells and that the pathway appears to involve, at least in part, a PKC- and Gi protein-dependent mechanism.

U937 cells deprived of endogenous annexin 1 demonstrate an increased PLA2 activity

Annexin 1 (An 1), a phospholipid and calcium binding protein, is strongly expressed in differentiated U 937 cells. In attempting to correlate the expression of An 1 with phospholipase A2 (PLA2) activity, U 937 cells were stably transfected both with a Sense and Antisense cDNA for An 1. PLA2 activity was measured by Flow cytometry analysis utilizing the bis-Bodipy-C11-PC fluorescent probe. U 937 cells stably transfected with the sense or antisense vectors were differentiated for 24 h with phorbol 12-myristate 13-acetate (PMA, 6 ng ml(-1)). Both in undifferentiated and differentiated cells, the Antisense clone (36.4 AS) showed consistently higher PLA2 activity than the control Sense clone (15 S). Since the fluorescent probe measures the total PLA2 activity, we used two different stimuli, PMA: (100 ng ml(-1)) or lipopolysaccharide (LPS, 10 ng ml(-1)), and two different inhibitors, to discriminate the PLA2 involved (namely arachidonyl trifluoromethyl ketone or AACOCF3, which is specific for the cytosolic PLA2, and SB 203347 specific for the secretory PLA2). In the Antisense clone the inhibitory effect of AACOCF was stronger [68%, P<0.025] than in the Sense, which may reflect the lower endogenous level of An 1 present in the cells. On the contrary, the inhibitory effect of SB 203347 [60% of inhibition] was identical in both clones. Since cPLA2 activity is correlated with its phosphorylation, Western and shift blot analysis were performed. They did not show any significative difference between the phosphorylated and non phosphorylated form of the enzyme in both the differentiated or not, Sense and Antisense clones. Furthermore the tyrosine phosphorylation analysis of An 1 showed that less than 10% of An 1 was phosphorylated irrespective of PMA presence or absence. From the pattern of inhibition observed, we propose that the endogenous unphosphorylated form of An 1 may act intracellularly to block the activity of a cytosolic PLA2.

Lipocortin 1 (annexin 1) in patches associated with the membrane of a lung adenocarcinoma cell line and in the cell cytoplasm

Lipocortin 1 (annexin I) is a calcium- and phospholipid-binding annexin protein which can be externalised from cells despite the lack of a signal sequence. To determine its cellular distribution lipocortin 1 in A549 human lung adenocarcinoma cells was localised by light- and electron-microscopic immunocytochemistry and by cell fractionation and western blotting. Lipocortin 1 immunoreactivity is concentrated in prominent patches associated with the plasma membrane. The intensity of these patches varied with the confluence and duration of the culture and was not detectably diminished by an EDTA wash before fixation. Tubulin and cytokeratin 8 were colocalized with lipocortin 1 in the patches. Within the cells lipocortin 1 was distributed throughout the cytoplasm. Electron microscopy revealed prominent immunoreactivity along the plasma membrane with occasional large clusters of gold particles in contact with the membrane surface of the cells; within the cytoplasm the membrane of some vesicle/vacuole structures and some small electron-dense bodies was immunoreactive, but no immunogold particles were associated with the multilamellar bodies. Subcellular fractionation, extraction and western blotting showed that lipocortin 1 in the membrane pellet was present as two distinct fractions; one, intimately associated with the lipid bilayer, which behaved like an integral membrane protein and one loosely attached which behaved like a peripheral membrane protein. The results show that a substantial amounts of lipocortin 1 is concentrated in focal structures associated with and immediately beneath the plasma membrane. These might form part of the mechanism by which lipocortin 1 is released from the cells.

Inhibitory effect of peptides derived from the N-terminus of lipocortin 1 on arachidonic acid release and proliferation in the A549 cell line: identification of E-Q-E-Y-V as a crucial component

1. The ability of the glucocorticoid-induced protein lipocortin 1 (LC1) to inhibit arachidonic acid release and cell proliferation in A549 cells may be mimicked by a sequence taken from the N-terminal, LC1(13-25) (FIENEEQEYVQTV). We have now synthesized and tested for biological activity a library of 25 smaller peptides derived from this sequence. 2. Peptides were tested in two assays: A549 cells were prelabelled with tritiated arachidonic acid and thapsigargin (50 nM) and EGF (10 nM) used to stimulate the release of this fatty acid. Cell proliferation was determined by counting cell numbers following 3 day incubation with these peptides, or controls. 3. Many of the peptides were highly insoluble but could be more readily dissolved in aqueous solution in the presence of commercial liposomes or phosphatidyl serine (5 microM). Since neither of these agents alone had any effect on arachidonic acid release or cell proliferation, all peptides were tested in the presence of 5 microM phosphatidyl serine. Under these conditions LC1(13-25) was active in both assay systems with an IC40 of 40.7 and 57.0 microM respectively. 4. Deletion of amino acids from the C-terminus of the peptide progressively diminished (2-3 fold) the molar potency of LC1(13-25) in both assays: after the removal of Val22 biological activity was virtually undetectable or very weak (< 30% of LC1[13-25]). 5. Removal of amino acids from the N-terminus also lead to a progressive reduction (3-5 fold) in the molar potency of the peptides and biological activity became undetectable, or very weak, after the removal of Glu18. 6. All active peptides contained the core sequence EQEYV(Glu-Gln-Glu-Tyr-Val) which seems to represent a crucial component of the pharmacophore, although this sequence on its own was inactive and the shortest peptide with significant activity was LC1(18-25) (EQEYVQTV). 7. Methoxylation of Tyr21 abolished the ability of LC1(18-25) to inhibit cell proliferation and arachidonic acid release. A cyclized version of LC1(18-25) was also tested and found to be inactive. 8. LC1(18-25) (178 microM) inhibits cPLA2 activation in A549 cells as judged by a band-shift assay, whereas equimolar concentrations of an inactive peptide LC1(19-25) were without effect in this assay system. 9. Several possible mechanisms whereby these peptides act are discussed in the light of LC1 biology and of the effect of glucocorticoids on cell function.